Rotatable x-ray grid with non-stationary center and method

ABSTRACT

A rotatable grid having a non-stationary center for allowing primary directed x-rays to pass through while preventing scattered secondary radiation from passing through the grid. A disc composed of aluminum or fiber strips interspaced with lead strips has an outer rim rotatably housed in a frame spaced over x-ray film. Compressed air is directed to strike recesses on the rim imparting rotation to the rim with respect to the frame. Four bearing assemblies, each having a roller adjustable from the rim edge and a roller supporting the bottom horizontal rim surface, are attached to the frame. A fastening device on each bearing assembly may be adjusted thereby changing the distance between the rim edge and the rim roller allowing the rotating disc center to move in a direction parallel with respect to the film surface.

United States Patent Cook [ 4] ROTATABLE X-RAY GRID WITH NON- STATIONARY CENTER AND METHOD [72] Inventor: William A. Cook, 925 S. Curry Pike,

Bloomington, Ind. 47401 [22] Filed: July 27, 1970 [21] App1.No.: 58,352

[52] US. Cl. ..250/62, 250/63, 250/105 [51] Int. Cl. ..G0ln 23/20 [58] Field of Search ..250/62, 63, 105

[56] References Cited UNITED sTATEs PATENTS 3,489,897 1/1970 Wainer ..250/62 FOREIGN PATENTS OR APPLICATIONS 759,534 2/1934 France ....250/63 [151 3,684,885 51 Aug. 15, 1972 Primary Examiner-Wi1liam F. Lindquist Attorney-Woodard, Weikart, Emhardt & Naughton [5 7] ABSTRACT A rotatable grid having a non-stationary center for allowing primary directed x-rays to pass through while preventing scattered secondary radiation from passing through the grid. A disc composed of aluminum or fiber strips interspaced with lead strips has an outer rim rotatably housed in a frame spaced over x-r'ay film. Compressed air is directed to strike recesses on the rim imparting rotation to the rim with respect to the frame. Four bearing assemblies, each having a roller adjustable from the rim edge and a roller supporting the bottom horizontal rim surface, are attached to the frame. A fastening device on each bearing assembly may be adjusted thereby changing the distance between the rim edge and the rim roller allowing the rotating disc center to move in a direction parallel with respect to the film surface.

6 Claims, 6 Drawing Figures Pmmmwms I912 3.684.885

SHEEI 2 or 3 INVENTOR W/LL/AM A. [0oz BY mum/m4 WWW/f WW7 ATTORNEYS PATENTEDws 15 i972 SHEET 3 [IF 3 INVENTOR WILLIAM A. Cook ATTORNEYS ROTATABLE X-RAY GRID WITH NON- STATIONARY CENTER AND METHOD BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to an apparatus for reducing secondary radiation from x-rays.

2. Description of the Prior Art When passing x-rays through a subject and exposing a film, the image thereon will be blurred or hazy since secondary or scattered radiation is produced by the subject. To eliminate this problem the Bucky Diaphragm was invented. Kurt Amplatz, M. D., Simple Bucky Diaphragm for High Speed Angiography, in American Journal Radiology 2: page 387, Nov/Dec 1967. Also see, Michel M. Ker-Pogossian, The Physical Aspects of Diagnostic Radiology, N.Y., Harper and Row, 1967, page 263, Library of Congress 66-19240.

Such a diaphragm is generally composed of strips of material opaque to scattered radiation interspaced between strips of material transparent to the primary radiation. The diaphragm is rotated, as in the following US. Pat. Nos: 1,609,475 to Janus, l,465,340 to Buck and 1,621,814 to Sawford, or may be reciprocated as in the following US. Pat. No.: 2,145,868 to Fisher and 3,163,989 to Maxwell.

It can be appreciated that in rotating a disc the center of the disc is stationary. Thus, in rotating a Bucky Diaphragm" the film immediately beneath the center of the diaphragm is subjected to secondary radiation and is therefore hazy and blurred. In addition, this area may be completely exposed or completely unexposed. Thus, there is a need for a structure for rotating an x-ray grid in such a manner so that the center of the grid is not stationary with respect to the film. The structure should allow the x-rays to pass through the grid center and should therefore avoid the center driving means utilized in the aforementioned reciprocating devices.

SUMMARY OF THE INVENTION The present invention is a rotatable x-ray grid having a non-stationary disc center. The grid has alternate strips of lead and aluminum or fiber for reducing scattered radiation through the grid to an x-ray film. The disc is enclosed in an outer rim housed in a frame with air tubes mounted thereon. Compressed air exits the air tubes striking recesses in the rim surface thereby causing the rim and disc to rotate with respect to the frame. Four bearing assemblies are attached to the frame adjacent the rim. Each bearing assembly has a roller abutting the bottom horizontal rim surface and a second roller adjustable to and from the rim edge. A fastening device secures the frame and bearing housing together and may be adjusted to change the distance between the rim edge and the rim roller thereby allowing the center of the disc to move in a direction parallel with the film surface.

It is an object'of the present invention to provide a rotatable x-ray grid having a non-stationary disc center and a method for obtaining a clear x-ray image on x-ray film beneath the grid and especially in the center.

Related objects and advantages of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an illustration of x-rays originating from a source, passing through a subject and onto a film. An xray grid incorporating the present invention is located between the subject and the film.

FIG. 2 is an enlarged view of the x-ray grid shown in FIG. I and viewed in the direction of arrows 2-2.

FIG. 3 is an enlarged view of the x-ray grid shown in FIG. I viewed along the line 3-3 and in the direction of the arrows.

FIG. 4 is a fragmentary enlarged section of one of the bearing assemblies shown in FIG. 2 and is taken along the lines 4-4 and viewed in the direction of the arrows.

FIG. 5 is a fragmentary enlarged view of a portion of the grid, rim and bearing assembly shown in FIG. 3 and is taken along the lines 5-5 and viewed in the direction of the arrows.

FIG. 6 is a perspective view of the grid of FIG. 1 without the rim or frame and particularly illustrates the layers of material in the grid.

DESCRIPTION OF THE .PREF ERRED EMBODIMENT For the purposes of promoting and understanding the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now more particularly to FIG. 1, there is illustrated a source 10 emitting x-rays 12 towards and through a subject 11 resting on table 9 and finally exposing the film in film container 15. The top of table 9 is made from a material, such as glass, which is transparent to x-rays. Subject 1] of course would be some portion of the patient such as, a hand or chest. Located between table 9 and film container 15 is a rotatable xray grid 13 having a non-stationary center. Rotating grid 13 is relatively transparent to x-rays l2 originating from source 10 and is relatively opaque to secondary radiation which impinges on the grid at angles different from that of transmitted x-rays 12. Thus, the radiation has a reduced level of scattered components once it passes through grid 13. Connected to grid 13 by tubes 58 and 59 is an air pressure source 16. Valve 17 allows the user to control the flow of air to grid 13.

FIG. 2 is an enlarged view of grid 13 taken in the direction of arrows 2-2 of FIG. 1. Grid 13 has a frame 20 supporting disc assembly 60 and four bearing assemblies 36, 37, 38 and 39. Disc assembly 60 has a disc 19 with a rim 21 around the disc perimeter. As may be seen from FIG. 3, the disc assembly is located in grid receiving hole 44 and extends through both sides of frame 20.

In the embodiment shown in FIG. 3, rotation is im parted to disc assembly 60 by air impinging on cusplike recesses 22 on the outer surface of rim 21. One or more air tubes may be utilized to distribute the air to the rim. As shown in F IG. 3, two air tubes 25 and 26 are provided with air, exiting outlet 23 in the direction of arrow 61 and outlet 24 in the direction of arrow 62 thereby causing disc assembly 60 to rotate in the direction of arrow 31. The outlet ends of the tubes should be positioned over rim 21 so as to not touch the rim while directing air at an angle downward towards recesses 22. Clamps 27 are fastened to frame 20 holding the air tubes in place. An air distribution box 28 is fastened to frame 20 and connects tubes 25 and 26 to the main air pressure source via nozzle 29. The nozzle is connected to tube 59 (FIG. 1) which is connected to valve 17 for controlling the flow of air to the rim.

The four bearing assemblies 36 through 39 shown in FIG. 2 allow disc assembly 60 to rotate with respect to frame 20. Bearing assembly 36 will now be described, it being understood that the bearing assemblies are identical and a similar description applies to bearing assemblies 37, 38, 39. It will be helpful to refer to FIGS. 2 through 4 in describing the bearing assembly. FIG. 4 is a section taken along the line 44 in the direction of the arrows of bearing assembly 36 illustrated in FIG. 2. Bearing assembly 36 has a body 52 secured to frame 20 by a screw 53 and bolt 50 or other such fastening devices. Screw 53 extends through frame 20 and into a blind threaded hole in body 52. Bolt 50 extends through a countersunk hole in frame 20 and body 52 and into complementary nut 49. A counterbore 51 in body 52 accomodates nut 49 and washer 48. As will be evident later, it is desirable to adjust the distance between the edge of disc assembly 60 and the bearing assembly. Thus, an elongated recess 47 (FIG. 3) and a slot 46 is provided in frame 20 allowing bolt 50, and the body of the bearing assembly to be moved to and from disc assembly 60.

Each bearing assembly has two rollers abutting the edge and horizontal surface of rim 21. For example, roller 42 (FIGS. 2 and 4) of bearing assembly 36 extends out and abuts against the horizontal surface 40 of rim 21 being freely rotatable on shaft 56. Roller 42 is kept in place by a head 54 attached to shaft 56 which is fixedly fastened through boss 55 to body 52. The second roller 43 of bearing assembly 36 is shown in FIGS. 3 and 4 abutting against the outside edge 41 of rim 21. Edge roller 43 is freely rotatable on a large diameter shoulder bolt 57 which passes through a U- shaped recess 63 in frame 20 and body 52 being threaded in a smaller diametered threaded hole in body 52. FIG. is a sectional view showing the relationship of the rim with respect to the two rollers and is taken along the line 55 of FIG. 3 and viewed in the direction of the arrows. Rim 21 has a shoulder 80 under a portion of roller 43 thereby preventing the disc assembly 60 from falling from frame in the direction of arrow 64. Of course, roller 42 prevents disc assembly 60 from falling from frame 20 in a direction opposite of arrow 64.

A perspective view of disc 19 is shown in FIG. 6 without its associated rim in order to illustrate the arrangement of the material in the disc. The disc has strips 66 of material opaque to x-rays interspaced between strips 65 of material transparent to x-rays. It has been found that the best results are obtained by making strips 66 from lead with a width of approximately 0.3mm and strips 65 from aluminum with a width of 005mm. The approximate thickness of the disc is 3.6mm. The disc may be attached to a rim by any number of means such as adhesives. The rim and frame may be made from metal such as aluminum.

With the disc assembly 60 rotating in the direction of arrow 30 (FIG. 2), arrow 31 (FIG. 3), and arrow 32 (FIG. 4), the edge roller will rotate in the direction of arrow 34 and roller 42 will rotate in the direction of arrow 33. It can be appreciated that when rotating a disc, the center of the disc remains in a stationary position. This causes a problem in the instant application in that the center of disc 19 will appear as a non-rotating point to the x-rays thus causing a dot or hazy area on the film. The above described structure precludes this from occurring by causing disc assembly 60 to rotate in such a manner so as to have a non-stationary center. Referring to FIG. 3, the dimension A is the distance between the rim edge 41 and the edge 67 of roller 43. Likewise, the dimension B is the distance between the rim edge 41 and the edge 68 of roller 69. By adjusting the distance between surface 67 of roller bearing assembly 36 and assembly 60 and the distance between surface 68 of roller bearing assembly 38 and disc assembly 60 until dimensions A and B each equal approximately 0.007 inches, a motion will exist relative to the center of the disc. This procedure can be accomplished by placing a feeler guage or shim having a thickness of 0.007 inches between edge 41 and edge 67 prior to tightening bolt 50 on bearing assembly 36. The bolt should then be tightened and the shim withdrawn. Likewise, the spacing for dimension B can be accomplished in a manner similar to that for the dimension A." As a result, center 18 of disc 19 will move between point and point 71 as the disc assembly rotates and moves from edge 68 of roller 69 to edge 67 of roller 43. The rollers of bearings 37 and 39 abut the rim edge in a running fit so as to not bind the disc in one position. Of course, the distance from point 70 to point 71 would equal 0.014 inches. Dimensions A and B may actually be each varied from 0.003 to 0.007 inches thereby allowing a total movement of center 18 from 0.006 to 0.014 inches. Good results have been obtained throughout the entire range of 0.006 to 0.0l4 inches. FIG. 3 has been exaggerated to show the spacing of dimensions A and B. Bearing assemblies 37 and 39 could be adjusted in a similar manner while having rollers 43 and 69 abutting the rim edge in a running fit. It would also be possible to have the edge rollers of all four bearing assemblies 36 through 39 adjusted slightly away from the rim edge. Hole 44 must be sufficiently larger than disc assembly 60 to allow for the motion. Of course, the force of the compressed air on rim 21 causes the disc to rotate and the center 18 to move.

The present invention contemplates and includes many variations of the above described structure. For example, a permanent magnet motor arrangement having two or three electro-magnets spaced at equal intervals around the periphery of the grid could be used to drive the disc assembly in lieu of the compressed air as described above. In addition, the number and type of bearings used around the periphery of the disc assembly may be changed from that which has been described. While the distance between the grid and the film may be varied, best results have been obtained when the grid is approximately 1 inch from the film.

It will be evident from the above description that the present invention provides a rotatable x-ray grid having a non-stationary center and a method for obtaining a clear x-ray image on x-ray film beneath the grid and especially in the center.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

The invention claimed is:

1. An x-ray grid allowing primary x-ray radiation to pass through to an x-ray film while excluding secondary scattered radiation comprising:

a rotatable disc allowing said primary x-ray radiation to pass therethrough;

a frame housing said disc;

power means to rotate said disc within said frame;

bearing assemblies mounted to said frame around said disc with at least one of said assemblies having a bearing spaced away from said disc to allow the center of said disc to move in a direction parallel to said film simultaneously as said disc rotates, each bearing assembly has a first and second bearing, said first bearing abuts the bottom surface of said disc, said second bearing is adjustable to and from the edge of said disc providing a bearing surface for said edge to contact; and wherein:

said disc has recesses around its edge;

said power means has an air tube directing compressed air to said recesses to force said disc to rotate.

2. The grid of claim 1 wherein:

said disc has strips of material opaque to said primary x-ray radiation interspaced with strips of material transparent to said primary x-ray radiation.

3. The grid of claim 2 wherein:

each of said bearing assemblies have a main body fastened to said frame, each of said first bearings are roller bearings rotatably mounted to said main body and extending under said disc, each of said second bearings are roller bearings rotatably mounted to said main body, said second bearings have longitudinal axes parallel with said edge of said disc.

4. The grid of claim 3 wherein:

said bearing assemblies are mounted to said frame relative to each other about said center of said disc, said second bearings of at least two of said bearing assemblies have outside surfaces spaced at least 0.003 inches from said edge of said disc.

5. A method of moving an x-ray grid with respect to x-ray film so as to obtain a clear x-ray image on said film immediately beneath the center of said grid comprising:

rotating said grid on bearings within a frame;

holding said frame still relative to said film;

spacing at least one of said bearings from the edge of said grid so said center moves relative to said film by at least 0.006 inches; and wherein:

compressed air is directed to said grid to rotate said 6. iiliiii? il o ii g primary x-ray radiation to pass through to an x-ray film while excluding secondary scattered radiation comprising:

a rotatable disc allowing said primary x-ray radiation to pass therethrough;

a frame housing said disc;

power means to rotate said disc within said frame;

bearing assemblies mounted to said frame around said disc with at least one of said assemblies having a bearing spaced away from said disc to allow the center of said disc to move in a direction parallel to said film simultaneously as said disc rotates; and wherein:

said disc has a rim with a first and second side and a circumferential edge with a continuous ledge projecting therefrom, said first side has recesses formed therein;

said power means is a source of pressurized gas directed into said recesses; and,

each of said bearing assemblies has a first and second bearing with said second bearing positioned adjacent said edge and ledge, said first bearings are mounted to said frame contacting said second side cooperatively with said second bearings mounting said disc in said frame.

UNITED STATES PATENT OFFICE Certificate Patent No. 8,684:,885 Patented August 15, 1972 William A. Cook Application having been made by William A. Cook, the inventor named in the patent above identified, for the issuance of a certificate under the provisions of Title 35, Section 256, of the United States Code, adding the names of Quentin J. Westrick and Joseph J. Bookstein as joint inventors, and a showing and proof of facts satisfying the requirements of the said section having been submitted, it is this 27th day of November 1973, certified that the names of the said Quentin J. Westriok and Joseph J. Boc)ckstleiin are hereby added to the said patent as joint inventors with the said William A. 00

FRED W. SHERLING, Associate Solicitor. 

1. An x-ray grid allowing primary x-ray radiation to pass through to an x-ray film while excluding secondary scattered radiation comprising: a rotatable disc allowing said primary x-ray radiation to pass therethrough; a frame housing said disc; power means to rotate said disc within said frame; bearing assemblies mounted to said frame around said disc with at least one of said assemblies having a bearing spaced away from said disc to allow the center of said disc to move in a direction parallel to said film simultaneously as said disc rotates, each bearing assemblY has a first and second bearing, said first bearing abuts the bottom surface of said disc, said second bearing is adjustable to and from the edge of said disc providing a bearing surface for said edge to contact; and wherein: said disc has recesses around its edge; said power means has an air tube directing compressed air to said recesses to force said disc to rotate.
 2. The grid of claim 1 wherein: said disc has strips of material opaque to said primary x-ray radiation interspaced with strips of material transparent to said primary x-ray radiation.
 3. The grid of claim 2 wherein: each of said bearing assemblies have a main body fastened to said frame, each of said first bearings are roller bearings rotatably mounted to said main body and extending under said disc, each of said second bearings are roller bearings rotatably mounted to said main body, said second bearings have longitudinal axes parallel with said edge of said disc.
 4. The grid of claim 3 wherein: said bearing assemblies are mounted to said frame 90* relative to each other about said center of said disc, said second bearings of at least two of said bearing assemblies have outside surfaces spaced at least 0.003 inches from said edge of said disc.
 5. A method of moving an x-ray grid with respect to x-ray film so as to obtain a clear x-ray image on said film immediately beneath the center of said grid comprising: rotating said grid on bearings within a frame; holding said frame still relative to said film; spacing at least one of said bearings from the edge of said grid so said center moves relative to said film by at least 0.006 inches; and wherein: compressed air is directed to said grid to rotate said grid relative to said film.
 6. An x-ray grid allowing primary x-ray radiation to pass through to an x-ray film while excluding secondary scattered radiation comprising: a rotatable disc allowing said primary x-ray radiation to pass therethrough; a frame housing said disc; power means to rotate said disc within said frame; bearing assemblies mounted to said frame around said disc with at least one of said assemblies having a bearing spaced away from said disc to allow the center of said disc to move in a direction parallel to said film simultaneously as said disc rotates; and wherein: said disc has a rim with a first and second side and a circumferential edge with a continuous ledge projecting therefrom, said first side has recesses formed therein; said power means is a source of pressurized gas directed into said recesses; and, each of said bearing assemblies has a first and second bearing with said second bearing positioned adjacent said edge and ledge, said first bearings are mounted to said frame contacting said second side cooperatively with said second bearings mounting said disc in said frame. 